Films are shown to recruited audiences long before release, and the results reshape endings, running times and marketing. What changes depends on which numbers the process actually produces.
The screening measures a few narrow things
Attendees are recruited to match a target demographic and watch an unfinished cut. Afterward they complete cards rating the film overall and indicating whether they would recommend it.
The headline figures are the share rating the film in the top categories and the share who would recommend it to a friend. Studios track these against benchmarks for comparable releases.
A smaller group stays for a moderated discussion. That conversation supplies the reasons behind the numbers, which the cards alone cannot provide.
Recommendation predicts word of mouth
Opening weekend attendance can be bought with advertising, but the following weekends depend on what early viewers tell others. The recommendation figure is a proxy for that.
A film with strong recommendation and weak overall scores is often left alone, because the enthusiasm of the audience that likes it matters more than broad approval.
The reverse pattern, wide mild approval with little enthusiasm, worries distributors most. It suggests a film that opens adequately and collapses.
Endings absorb the most changes
Audiences leave with the ending freshest, and it weighs heavily on the cards. It is also, practically, the cheapest major element to change with reshoots.
Ambiguous conclusions test poorly with general audiences and are often resolved. Deaths of sympathetic characters are frequently reversed for the same reason.
Filmmakers with contractual final cut can decline these changes. Most do not have it, and the studio's contractual authority over the release version is the deciding factor.
Pacing complaints translate into runtime cuts
Discussion groups reliably report a middle section that drags, and editors respond by tightening or removing subplots.
Shorter runtimes also allow more daily showtimes, which increases capacity on opening weekend. The commercial and creative arguments point the same direction.
Material cut this way often reappears in home releases, where the constraint does not apply and the longer version becomes a selling point.
Marketing learns more than the film does
Cards ask what attendees would tell a friend the film is about. Those phrases feed directly into trailers and taglines.
Screenings also reveal which characters or scenes registered most strongly, which is why a trailer can foreground a supporting performance that occupies little screen time.